1. Field of the Invention
The present invention relates to optical scanners and more particularly relates to a scanning mechanism capable of scanning both opaque and transparent materials, wherein a representative of the opaque materials may be a page from a book and a representative of the transparent materials may be an X-ray film.
2. Description of the Related Art
There are many applications that need optical scanners to convert paper-based objects, such as texts and graphics, to an electronic format that can be subsequently analyzed, distributed and archived. One of the most popular optical scanners is flatbed scanners that typically convert scanning objects, including pictures and papers, to images that can be used, for example, for building World Wide Web pages and optical character recognition. Another emerging optical scanner is what is called sheet-fed scanners that are small and unobtrusive enough to sit between a keyboard and a computer monitor or integrated into a keyboard to provide a handy scanning means. Most optical scanners are referred to as image scanners as the output thereof is generally in digital format.
Both the flatbed and sheet-fed scanners are designed for scanning sheet-like scanning objects, such as pictures or pages of an article. The scanners generally include a sensing module that is responsible for converting the scanning objects optically into electronic images. The sensing module further includes an illumination system, an optical system, an image sensor and an output circuit. The illumination system is used to illuminate the scanning object that is being scanned. The optical system is used to direct and focus the light reflected from the scanning object onto the image sensor. The image sensor comprises a plurality of photodiodes or photo-capacitors, referred to as photo-detector hereafter, that are sensitive to light and produce proportional pixel signals accordingly. Therefore corresponding pixel signals are produced in the image sensor when the reflected light is focused thereon and the output circuit is used to convert the pixel signals to an appropriate format to be processed or stored in subsequent systems.
In many cases, there is a need to convert transparent objects, such as negative or positive films, transparencies for a overhead projector or X-ray films, into images so that the information in the transparent objects can be, for example, electronically analyzed, distributed or archived. The conversion is currently done through a specially designed film scanner, often bulky and run by a separate service. As portable scanners are evolving to become an accessory to a laptop computer and more people start to carry a one, there is a great need for a portable scanning device that is capable of scanning not only the regular papers but also the transparent materials. The demand for portable scanners with the dual-scanning capability is ever increasing in both consumer and business markets.